1. Field of the Invention
The invention relates to a touch device, and more particularly to an optical touch device and locating method thereof.
2. Description of the Related Art
Referring to FIG. 1, a conventional optical detection system disclosed in Taiwanese Patent Publication No. 201030578 is shown to include a processing unit (not shown), and two modules 11, 12 respectively oriented toward an detection area 10 and disposed respectively at an upper right corner and an upper left corner of the detection area 10. Each of the modules 11, 12 includes a detection unit 111, 121. The detection unit 111 includes a guiding lens 112 with a focus (F), and a detector 113. The detection unit 121 includes a guiding lens 122 with a focus (F), and a detector 123. Each of the guiding lenses 112, 122 has an axis 115, 125. A distance (S) is formed between centers 114, 124 of the guiding lens 112, 122 and is equal to the length of a line 13. An included angle (θ1) is formed between an axis 115 of the guiding lens 112 and the line 13. An included angle (θ2) is formed between an axis 125 of the guiding lens 122 and the line 13.
When an object 2 touches the detection area 10, the object 2 reflects part of light from a light-generating unit (not shown) into two reflected lights 21, 22. The reflected lights 21, 22 respectively pass through the guiding lenses 112, 122, thereby forming respectively two images 23, 24 on the detectors 113, 123. An included angle (Δθ1) is formed between the axis 115 and the reflected light 21. An included angle (Δθ2) is formed between the axis 125 and the reflected light 22. The image 23 is formed at a position away from an intersection point of the detector 113 and the axis 115 by a distance (ΔL1). The image 24 is formed at a position away from an intersection point of the detector 123 and the axis 125 by a distance (ΔL2). Thus, the processing unit obtains an included angle (β1) formed between the reflected light 21 and the line 13, and an included angle (β2) formed between the reflected light 22 and the line 13 using the following Equations (1) and (2):
                              Δθ          n                =                  arctan          ⁡                      (                                          Δ                ⁢                                                                  ⁢                                  L                  n                                            F                        )                                              (        1        )                                                      β            n                    =                                    θ              n                        -                          Δθ              n                                      ,                            (        2        )            where n=1, 2. Thereafter, the processing unit can determine a touch location of the object 2 in the detection area 10 based on β1, β2 and S.
However, for such a configuration, it is required to compute inverse trigonometric functions and then proceed triangulation computation, thereby resulting in relatively complicated computation. Therefore, improvements may be made to the above techniques.